Breaking and Entering isn't a crime?

The Monrovia Police Department knows me on a first-name basis.

As some of you may be aware, the lease agreement I signed with my current landlord leases me the entire first floor of the building (minus the stairs to get to the second story). This includes the only laundry room in the fourplex, which has an exterior door accessible from the alley and an interior door accessible from the kitchen. There's a catch, however; the laundry room is open to all residents between the hours of 8 AM and 8 PM. If the residents would respect this, we wouldn't have a problem. However, in the year I've lived here, I'd say there were people attempting to do laundry well past 9 PM (when I lock the door) 50% of the time.

Last night, I locked the outside door at 9 PM. There was laundry in the dryer that had nearly just started, and it belonged to a neighbor who had been warned about the rule multiple times, starting from day 4 of my residency when she was trying to do start a load at 11:30 at night. Well, she showed up around 9:45 and began banging on the door. I walked into the laundry room from the kitchen and informed her that it was past time, that the door was locked, and that she could collect the laundry in the morning. She screamed that I couldn't do that, and that the laundry room was common property. I corrected her by saying that I rented the room, I paid the electricity and gas, and that I had a right to lock the door via my lease agreement. It was at this point that she tried to kick down the door.

"After talking with the police for about 45 minutes on the telephone..." or rather, after calling the police and waiting for 45 minutes, having an officer come out and look at the door, we came to the conclusion that she'd not actually committed any crimes against me, and that the only visible crime committed was misdemeanor vandalism against the landlord, who owned the door. I asked whether this constituted breaking and entering, and was informed that no such law existed. This was news to me, but I let it go.

I talked with the landlord today, and he says that he doesn't plan to file charges, and that I should "keep a low profile" when dealing with the neighbor. He insists that he's got something bigger planned for her, but I don't believe it.

So, all you legal scholars out there, any advice as to my next course of action?